invisible leaks

Study: US oil and gas methane emissions have been dramatically underestimated

Using better equipment can reduce leakages, capture valuable gas.

Megan Geuss – Jun 22, 2018 11:58 am | 48

A natural gas facility stands on the Pinedale Anticline on May 3, 2018 in Pinedale, Wyoming. (Photo by Melanie Stetson Freeman/The Christian Science Monitor via Getty Images) Credit: Getty Images

The US has been dramatically underestimating methane emissions from oil and gas operations, according to a new study published in Science on Thursday. The study, conducted by the Environmental Defense Fund and 15 partner universities, asserts that methane emissions from oil and gas production are likely 63 percent higher than what the Environmental Protection Agency has reported.

The discrepancy stems from the way methane is measured and monitored, the authors suggest. Methane leakages are measured at known intervals and at specific parts of equipment, without verification of the leak volume at the facility as a whole. This allows the industry to avoid counting any surprise leakage events, which the authors claim are more common than not.

The results are concerning because methane is a potent greenhouse gas that has more of a warming effect in the atmosphere than carbon dioxide, part for part. On the other hand, methane is shorter lived in the atmosphere than carbon dioxide, so restricting its escape can have positive short-term effects on warming.

This creates a difficult situation: methane is the main component of natural gas, and natural gas burns cleaner than coal and has largely contributed to coal’s demise. Though burning natural gas results in fewer pollutants released to the atmosphere, if the gas is released before it’s burned, the methane can be severely environmentally damaging. In addition, leaking natural gas is something of an economic waste, too: any amount of the colorless, odorless gas that escapes obviously can’t be sold. Though natural gas is cheap right now, fixing natural gas leaks can have monetary benefit over time.

New information

The authors conducted facility-specific measurements at more than 400 well pads and “scores” of midstream facilities with the cooperation of 50 oil and gas companies. They paired this data with aircraft observations of areas that contained about 30 percent of US natural gas production.

When the researchers scaled up their results to a national level, they estimated that US natural gas production is releasing gas equivalent to 2.3 percent of gross US national gas production. That number is 63 percent higher than the 1.4 percent the EPA had previously estimated. The New York Times points to a 2017 study that found that once the natural gas leakage rate hit between four and five percent of gross US natural gas production, natural gas is about equivalent to burning coal from a climate perspective.

This week’s paper contends that such a vast difference from the EPA numbers can’t be attributed to the uncertainty in the estimate or to some temporary fluke in the instruments. Instead, underestimation of methane release is systematic. Current industry measurement practices “miss high emissions caused by abnormal operating conditions,” like equipment malfunction. For example, the study says that measurement teams generally don’t measure the leakage rate of venting tanks because getting close to a venting tank is dangerous, and measurement is technically difficult without an aerial survey.

Omitting leak measurements of malfunctioning equipment can cause bias in the officially published data. The authors conducted aerial surveys of 8,000 production sites around the US and found that approximately four percent “had one or more observable high emission-rate plumes.”

“Emissions released from liquid storage tank hatches and vents represented 90 percent of these sightings,” the study claims. “It appears that abnormal operating conditions must be largely responsible, because the observation frequency was too high to be attributed to routine operations like condensate flashing or liquid unloadings alone.”

A problem with a solution

The authors say that these methane emissions represent a problem that has a relatively painless solution. The leaking natural gas as a whole constitutes about $2 billion per year in sales, and continuing leaks “significantly erode the potential climate benefits of natural gas use.”

To get back that money and that environmental benefit, oil and gas producers merely need to adopt a few well-established technologies and practices to identify and stop leaks on-site. These technologies include “optical gas imaging, deployment of passive sensors at individual facilities or mounted on ground-based work trucks, and in situ remote sensing approaches using tower networks, aircraft or satellites,” the paper states. More frequent observation of leaks, the authors argue, will result in better-studied leaks and, consequently, better-engineered technology to prevent leaks.

Minority opposition to the solution

Methane leaks and venting in the oil and gas industry have been a concern for years. However, the Trump administration has been opposed to quantifying the leaks and enforcing best practices despite general support for fewer methane emissions and less resource waste.

In early 2017, the Senate voted 51-49 not to scrap an Obama-era rule allowing the Bureau of Land Management (BLM) to adopt methane release standards for oil and gas producers on federal and tribal lands. The vote was surprising because it garnered the support of a few Republicans at a time when similar legislative actions were unyieldingly partisan. The Republican senators who stepped away from their party opposed the leak of valuable resources that, if captured and sold, would generate royalties for their states.

Later, however, the Department of the Interior moved to suspend the rule while exploring ways to weaken or eliminate it. The DOI’s action was challenged in court, and in February a US District court blocked the department’s suspension of the rules.

Similarly, the EPA, led by Administrator Scott Pruitt, has resisted any enforcement of methane emissions standards. The agency has tried to freeze its own rules limiting methane emissions, and, in April, fourteen states sued the agency for freezing enforcement of Obama-era rules that would have regulated methane leaks under the Clean Air Act.

Science, 2018. DOI: 10.1126/science.aar7204 (About DOIs).

Listing image: Getty Images

Megan Geuss Staff editor

Megan is a staff editor at Ars Technica. She writes breaking news and has a background in fact-checking and research.

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